Measurement of multipath interference in the coherent crosstalk regime

We compare various techniques to measure multipath interference (MPI) in devices exhibiting distributed coherent crosstalk. A notable example of devices in this class is the higher order mode dispersion compensator. These devices are susceptible to deterministic noise as well as intermittent fading, and the measurement technique employed must capture both these manifestations of MPI. We show that, ultimately, slow temporal intensity variations of a continuous-wave distributed-feedback laser yields the best measure of MPI in few-mode fiber devices.